During the fabrication of microcircuits, the precise positioning of a number of appropriately doped regions on a slice of semiconductor is typically followed by the positioning of one or more interconnection patterns on the semiconductor. Positively doped resists have been extensively used as masking materials to delineate patterns onto a substrate so that the patterns can be subsequently etched into, or otherwise defined in, the substrate. The final steps in preparing the substrate then involve removing the unexposed resist material and any etching residue, if etching was used, from the substrate. It is critical that as much as possible of the residue and resist be removed to provide a wafer having sufficient integrity for subsequent use of the wafer in microcircuitry.
A semiconductor integrated circuit has very fine structures. The fine circuits are generally fabricated by: uniformly coating a photoresist on an insulating film or a conductive film (such as an oxide film, an Cu film, or Al alloy film) coated on a substrate; exposing and developing the photoresist to form a certain pattern; etching the substrate, or depositing a film thereon, by using the patterned photoresist as a mask; and thereafter removing the unnecessary photoresist.
Additionally, plasma etching, reactive ion etching, or ion milling are also used to define the pattern in a substrate. During such etching processing, an organometallic by-product compound can be formed on the sidewall of the substrate material. A recently developed technique effective for photoresist removal is plasma oxidation, also known as plasma ashing. However, while this process is effective for removing a photoresist, it is not effective for removing the organometallic polymer formed on the sidewall of the substrate during the etching process.
Polyimides are increasingly used in microelectronics as fabrication aids, passivants, and inter-level insulators. The use of a polyimide as a fabrication aid includes application of the polyimide as a photoresist, planarization layer in a multi-level photoresist scheme, and as an ion implant mask. In these applications, the polymer is applied to a wafer or substrate, subsequently cured or patterned by a suitable method, and removed after use. Many conventional strippers are not sufficiently effective in removing the polyimide layer once the polyimide has been subjected to curing. The removal of such polyimides is normally accomplished by boiling the substrate in hydrazine or exposure to oxygen plasma.
The stripping and cleaning compositions of the present invention remove photoresists without attacking the substrates themselves, particularly metal substrates such as copper, aluminum, titanium/tungsten, aluminum/silicon, aluminum/silicon/copper; substrates such as silicon oxide, silicon nitride, and gallium/arsenide; and plastic substrates such as polycarbonate. The requirement for a cleaning solution to remove all types of residue generated as a result of resist layers and etching of various types of metals, such as aluminum, aluminum/silicon/copper, titanium, titanium nitride, titanium/tungsten, tungsten, silicon oxide, polysilicon crystal, etc., presents a need for more effective cleaning chemistry in the processing area.
In addition to removing as completely as possible the resist material, particularly with the introduction of submicron process techniques to form wafers, there is a demand for cleaning technology for removing etching residue remaining following resist removal. Unfortunately, it has been found that no single cleaner is universal, in that it can clean the required materials without adversely affecting or hindering subsequent manufacturing operation or process steps involving the substrate. The requirement for a cleaning solution to remove photoresists and other residue of various types of metals, such as aluminum, aluminum/silicon/copper, titanium, titanium nitride, titanium/tungsten, tungsten, silicon oxide, polysilicon crystal, low-k materials, etc., presents a need for more effective cleaning chemistry in the processing area.
Known photoresist stripper compositions containing a combination of a polar solvent and an amine compound include:                1. U.S. Pat. No. 4,403,029 describes alkaline/solvent mixtures useful as photoresist strippers, but not necessarily cleaners, that include dimethylacetamide or dimethylformamide and alkanolamines.        2. U.S. Pat. Nos. 4,428,871, 4,401,747, and 4,395,479 describe cleaners containing 2-pyrrolidone, dialkylsulfone and alkanolamines.        3. U.S. Pat. No. 4,744,834 describes cleaners containing 2-pyrrolidone and tetramethylammonium hydroxide. Such stripping compositions, however, have only proven successful in cleaning “sidewall polymer” from the contact openings and metal line etching in simple microcircuit manufacturing involving a single layer of metal when the metal structure involves mainly Al—Si or Al—Si—Cu and the residue that contains only an organometallic compound with aluminum.        4. U.S. Pat. No. 4,617,251 teaches a positive photoresist stripping composition containing (A) a selected amine compound (e.g., 2-(2-aminoethoxy)-ethanol; 2-(2-aminoethylamino)-ethanol; or a mixture thereof) and (B) selected polar solvents (e.g., N-methyl-2-pyrolidinone, tetrahydrofurfuryl alcohol, isophorone, dimethyl sulfoxide, dimethyl adipate, dimethyl glutarate, sulfolane, gamma-butyrolactone, N,N-dimethylacetamide or mixtures thereof). The reference further teaches that water as well as dyes or colorants, wetting agents, surfactants and antifoamers may be added into this composition.        5. U.S. Pat. No. 4,770,713 teaches a positive photoresist stripping composition containing (A) a selected amide (e.g., N,N-dimethyl acetamide; N-methyl acetamide; N,N-diethyl acetamide; N,N-dipropyl acetamide; N,N-dimethyl propionamide; N,N-diethyl butyramide or N-methyl-N-ethyl propionamide) and (B) a selected amine compound (e.g., monoethanolamine, monopropanolamine, or methyl-aminoethanol). The patent also teaches this stripper may optionally contain a water miscible nonionic detergent (e.g., alkylene oxide condensates, amides or semi-polar nonionics).        6. U.S. Pat. No. 4,824,763 teaches positive-working photoresist stripping composition containing (A) triamine (e.g., diethylene-triamine) and (B) a polar solvent (e.g., N-methyl-2-pyrrolidone, dimethylformamide, butyrolactone, aliphatic hydrocarbons, aromatic hydrocarbons, or chlorinated hydrocarbons).        7. U.S. Pat. No. 4,904,571 teaches printed circuit board photoresist stripper composition containing (A) a solvent (e.g., water, alcohols, ethers, ketones, chlorinated hydrocarbons or aromatic hydrocarbons); (B) an alkaline compound dissolved in said solvent (e.g., primary amines, secondary amines, tertiary amines, cyclic amines, polyamines, quaternary ammonium amines, sulfoniumhydroxides, alkali hydroxides, alkali carbonates, alkali phosphates or alkali pyrophosphates); and (C) a borohydride compound dissolved in said solvent (e.g., sodium borohydride, lithium borohydride, dimethyl amine borone, trimethyl amine borone, pyridane borone, tert-butyl amine borone, triethyl amine borone, or morpholine borone).        8. U.S. Pat. No. 5,102,777 teaches a positive photoresist stripper composition comprising (A) a solvent (e.g., a pyrrolidone compound, a diethylene glycol monoalkyl ether, a sulfur oxide compound, a sulfolane compound or a mixture thereof); (B) an amine (e.g., alkanolamine); and (C) a fatty acid (e.g., capric acid, lauric acid, talmitric acid, caprylic acid, myristic acid, oleic acid, stearic acid, linoleic acid, linolic acid, buthylic acid, abietic acid, isooctoic acid, isohexadecanoic acid, isostearic acid, behenic acid, undecylenic acid, hydroxystearic acid, chipanodonic acid, arachidonic acid, oleostearic acid, or 2-ethylhexadecanilic acid).        9. U.S. Pat. No. 5,279,791 teaches a stripping composition for removing resists from substrates containing (A) hydroxylamine; (B) at least one alkanolamine; and optionally (C) at least one polar solvent.        10. U.S. Pat. No. 5,308,745 teaches an alkaline-containing photoresist stripping composition comprising (A) a stripping solvent (e.g., 2-pyrrolidinone, 1-methyl-2-pyrrolidinone, 1-ethyl-2-pyrrolidinone, 1-propyl-2-pyrrolidinone, 1-hydroxyethyl-2-pyrolidinone, 1-hydroxypropyl-2-pyrrolidinone, diethylene glycol monoalkyl ethers, dialkyl sulfones, dimethyl sulfoxide, tetrahydrothiophene-1,1-dioxides, polyethylene glycol, dimethylacetamide or dimethylformamide; (B) a nucleophilic amine (e.g., 1-amino-2-propanol, 2-(2-aminoethoxy) ethanol, 2-aminoethanol, 2-(2-aminoethylamino)-ethanol or 2-(2-aminoethylamino) ethylamine); and (C) a non-nitrogen containing weak acid (e.g., acetic acid, phthalic acid, 2-mercaptobenzoic acid, 2-mercaptoethanol, 1,3,5-trihydroxybenzene, pyrogallol, resorcinol, 4-tert-butylcatechol, carbonic acid or hydrofluoric acid).        11. U.S. Pat. No. 5,334,332 teaches a photoresist resist stripping and cleaning composition comprising (A) hydroxylamine; (B) at least one alkanolamine; (C) water; (D) optionally, at least one polar solvent; and (E) optionally, a chelating reagent (e.g., thiophenol, ethylenediamine tetraacetic acid or 1,2-dihydroxybenzene) to reduce the surface metal contamination on wafers.        12. U.S. Pat. No. 5,399,464 teaches a stripping composition for removing positive organic photoresist from a substrate comprising (A) a triamine (e.g., diethylene triamine); (B) a nonpolar or polar organic solvent (e.g., N-methyl pyrrolidone).        13. U.S. Pat. No. 5,417,802 teaches a material useful for photoresist removal or post-metal etch clean up that comprises (A) a primary or secondary amine; (B) a solvent (e.g., dimethyl sulphoxide or dimethylacetylamide); and (C) organic ligands such as crown ethers or cyclodextrines.        14. Japanese Patent Application No. 63-208043 teaches a positive-working photoresist stripper composition containing (A) 1,3-dimethyl-2-imidazolidinone; (B) a water-soluble organic amine (e.g., monoethanolamine, 2-(2-aminoethoxy)-ethanol, or riethylenetetramine). The application also teaches a surfactant may be added to the stripper.        15. Japanese Patent Application No. 64-081949 teaches a positive-working photoresist stripper composition containing (A) a solvent (e.g., gamma-butyrolactone, N-methyl-formamide, N,N-dimethylformamide, N,N-dimethyl-acetamide or N-methylpyrrolidone); (B) an amino alcohol (e.g., N-butyl-ethanolamine or N-ethyldiethanolamine); and (C) water.        16. Japanese Patent Application No. 4-350660 teaches a stripper for positive photoresists comprising (A) 1,3-dimethyl-2-imidazolidinone (DMI), (B) dimethylsulfoxide (DMSO), and (C) a water-soluble amine (e.g., monoethanolamine or 2-(2-amino-ethoxy)ethanol), wherein the amount of the water-soluble amine is 7-30% by weight.        17. Japanese Patent Application No. 1999-197523 describes a stripper composition for photoresist used in manufacture of liquid crystal display device that includes 5-15 weight % of alkanolamine, 35-55% sulfoxide or sulfone compound, and 35-55 wt. % glycol ether.        18. Japanese Patent Application No. 08087118 describes a stripper composition that includes 50-90 weight % of alkanolamine, and 50-10% dimethyl sulfoxide or N-methyl-2-pyrrolidone.        19. Japanese Patent Application No. 03227009 describes a stripper composition that includes ethanolamine and dimethyl sulfoxide.        20. Japanese Patent Application No. 07069619 describes a stripper composition that includes alkanolamine, dimethyl sulfoxide, and water.        21. U.S. Pat. No. 5,480,585 and Japanese Patent Hei. 5-181753 disclose organic strippers comprising alkanolamine, a sulfone compound or a sulfoxide compound, and a hydroxyl compound.        22. The Japanese Laid-open Patent No. 4-124668 discloses a photoresist stripping composition including 20-90% by weight of an organic amine, 0.1-20% by weight of phosphoric ester surfactant, 0.1-20% by weight of 2-butyne-1,4-diol, and the remainder glycol monoalkylether and/or an aprotic polar solvent.        23. The Japanese Laid-open Patent Sho. 64-42653 discloses a photoresist stripping composition comprising over 50% by weight of dimethylsulfoxide (more desirably over 70% by weight), 1 to 50% by weight of a solvent such as diethyleneglycol monoalkylether, diethyleneglycol dialkylether, gamma-butyrolactone or 1,3-dimethyl-2imidazoledinone, and 0.1-5% by weight of a nitrogen-including organic hydroxyl compound, such as monoethanolamine. The reference recites that the amount of dimethylsulfoxide less than 50% by weight causes great reduction in stripping force, while the amount of nitrogen-including organic hydroxyl compound solvent over 5% by weight corrodes the metal (e.g., aluminum) film.        24. U.S. Pat. No. 5,091,103 to Dean et al. teaches a positive photoresist stripping composition containing: (A) N-alkyl-2-pyrrolidone; (B) 1,2-propanediol; and (C) tetraalkylammonium hydroxide.        
Depending on the constituents of the compositions and the ratio thereof, the aforementioned stripping compositions exhibit greatly different characteristics in photoresist stripping force, metal corrosion properties, the complexities of a rinsing process following the stripping, environmental safety, workability and price. Several commercial products are now available to clean the photoresist and plasma etching residues left by plasma etching followed by oxygen ashing. For example, EKC 265, available from EKC Technology, Inc., is a plasma etching cleaning solution composed of water, alkanolamine, catechol and hydroxylamine. Such a composition is disclosed in U.S. Pat. No. 5,279,771.
Although these commercial products can dissolve photoresist and plasma-etching residues, the combination of water and alkanolamine contained therein can also attack the metallic layers deposited pattemwise on the substrate. The addition of a corrosion inhibitor to these products can mitigate the unwanted attack on the metallic layers and oxide layers deposited on the substrate. However, even in the presence of a corrosion inhibitor, they may attack certain corrosion-sensitive metal layers such as copper, aluminum or aluminum alloys (e.g., Al—Cu—Si), titanium nitride, titanium tungsten, and the like.
Additionally, many conventional post-etch cleaning compositions, including amine/solvent, hydroxylamine, fluoride, or choline hydroxide-based compositions, are not completely compatible with major low-k dielectric materials, such as hydrogen silsesquioxane (HSQ). The dielectrics may irreversibly and excessively change their physical dimensions and/or electrical/physical/chemical properties after treatment with these cleaning compositions. The changes may subsequently cause process, yield, and reliability problems in semiconductor devices.
The conventional post-etch cleaning compositions can also have problems in compatibility or cleaning in metal structures formed by high density plasma etch in a subtractive process. The post-etch residue can be difficult to clean and the metals can be prone to corrosion.
In addition, many of the conventional compositions contain highly toxic substances which can cause environmental/health/safety concerns, in areas such as wafer cleaning processes, manufacturing/QC/transport, and waste treatment/disposal. Some compositions can also pose issues in other areas, such as cost of the raw materials used as well as manufacturing/wafer cleaning/disposal process/equipment required, manufacturability, or aesthetics (some compositions have or contain substances of strong and unpleasant odors).
It is difficult to balance effective plasma etching residue removal and corrosion inhibition because chemical compositions of the plasma etching residues are generally similar to those of the metal layers or oxide layers on the substrate. The alkanolamine used in the prior art cleaning compositions was often times found to attack both the plasma etching residues and the substrate metal layers in the presence of water. Water is often present as a contaminant, for example from the atmosphere, from wet components, and the like, and may even be released from certain photoresist structures during dissolution. The problem of wafer-cleaning composition-induced corrosion has resulted in manufacturers resorting to use of alcohol or some other solvent, for example isopropyl alcohol, to remove the cleaner.
Moreover, if a post-cleaner rinse such as isopropyl alcohol was not used, the corrosion could be very severe. In addition, some types of the corrosion inhibitors have been found to retard plasma etching residue removal and other treatments. There is a need for strippers that are useful with corrosion-prone metal substrates, particularly for copper substrates, which do not corrode metal substrates in the presence of small quantities of water.